This invention relates generally to a rapid leak detection apparatus and method for underground fluid systems and more particularly to an apparatus and method for the rapid detection and location of leaks from underground gasoline storage tanks.
It is standard in the oil industry to employ pressure tests, various types of still gauging, or liquid level measurements or to perform measurements of hydrocarbons in the subsurface to determine if a buried tank is leaking. Each of these conventional methods suffers significant practical shortcomings. The pressure tests are known to be insensitive and thus are not reliable. The still gauging methods require the tank to be filled with product to a point above ground where changes in liquid level are observed in a small diameter tube while monitoring for the product temperature to subtract thermal expansion or shrinkage effects. The major drawbacks to this method are inconvenience due to disruption of tank service for about twelve hours and the expense for testing and for the purchase of sufficient product to fill the potentially leaking tank.
The method of testing for hydrocarbons in the subsurface is known to be highly unreliable due partially to the fact that surface spills create relatively high subsurface product vapor concentrations. Thus the vapor detection method of leak sensing is seldom considered as reliable, let alone conclusive.
Once the presence or existence of a leak has been confirmed, the location of the leak is normally or typically determined by the time consuming and expensive process of excavating the entire area around the tank or by undertaking a time consuming soil sampling procedure. The sampling procedure requires soil coring at numerous potential leak locations followed by expensive laboratory analysis of the test soil cores for hydrocarbons.
The technique proposed herein offers a vastly more sensitive and faster tracer leak detector system that circumvents substantially all of the shortcomings and problems of the prior art.